In the recent years, the driving circuit of integrated display is becoming a hotspot in research of flat panel display. Driving circuits of integrated display refer to integrating peripheral circuits including gate driving circuits and data driving circuits which are in form of thin film transistors (TFT), disposed onto display panels where TFT pixels are located, so that the number of peripheral driving ICs, the packaging process, and the manufacturing cost are reduced. In addition, peripheries of the displays are slimmed down, modules of the displayer can be arranged in a more compact manner, and mechanical and electrical reliabilities are enhanced.
In driving circuits of displays, shift register units are important cell modules of gate driving circuits. In designs of shift register units, low voltage maintaining circuits are usually needed to guarantee that signal output terminals connected to row scanning line would not be in floating state, and to eliminate low voltage noise due to clock feedthrough and capacitive coupling. However, in low voltage maintaining circuits, transistors for maintaining low voltage are subject to threshold voltage shift due to long time voltage pressure. Such degradation of transistors may lead to failure of circuits after long time of work. Threshold voltage shift of low voltage maintaining transistors may be more severe for those shift register units which are based on technical solutions with amorphous silicon, which may influence the life span of the circuits.
In order to ensure good liability of shift register units, in present solutions, lowing of voltage pressures, bias of impulse voltages, reduction of duty cycles, and other means are applied to reduce the amount of threshold voltage shift of the low voltage maintaining transistors, and to extend the life span of circuits. In middle and large size panel displays, driving circuits have to work for extended hours, which is more challenging to the life span of circuits. Thus, it is a topic worthwhile for further research regarding how to efficiently increase circuit working time and increase life span of shift registers.